How do I write raw pixel data and save as a bitmap

Question

My problem is this: I wanna try to make a white color 24bit bitmap, but everytime I write to the bmp file, it gives me white black/white stripes. i dont understand why? Maybe i skip some bytes? If you want more information on the code just ask.

setup settings:

void setup_settings( ) {
 // information om billedet
 pic.infoHeader.biSize = sizeof(BMP_InfoHeader);
 pic.infoHeader.biBitCount = 24;
 pic.infoHeader.biWidth = WIDTH;  // Hoejte i pixels
 pic.infoHeader.biHeight = HEIGH; // bredte i pixels
 pic.infoHeader.biPlanes = 1;
 pic.infoHeader.biCompression = 0;
 pic.infoHeader.biSizeImage = WIDTH * HEIGH * (pic.infoHeader.biBitCount/8);
 pic.infoHeader.biXPelsPerMeter = 0;
 pic.infoHeader.biYPelsPerMeter = 0;
 pic.infoHeader.biClrUsed = 0;
 pic.infoHeader.biClrInportant = 0;

 pic.fileHeader.bfType[0] = 'B';
 pic.fileHeader.bfType[1] = 'M';
 pic.fileHeader.bfReservered1 = pic.fileHeader.bfReservered2 = 0;
 pic.fileHeader.bfOffBits = sizeof(BMP_FileHeader) + pic.infoHeader.biSize;
}

this funktion definition for my SaveBitmapFile is:

int SaveBitmapFile(const std::string filename, bit24* image){
// gem filen
std::ofstream writer(FileName.c_str(), std::ofstream::binary);

if(!writer.is_open()){
    printf("Error: While Writing\n");
    return -1;
}
writer.write(reinterpret_cast<char *>(&pic.fileHeader), sizeof(BMP_FileHeader) );
writer.write(reinterpret_cast<char *>(&pic.infoHeader), sizeof(BMP_InfoHeader) );
writer.write(reinterpret_cast<char*>(&image[0]), pic.infoHeader.biSizeImage);
writer.close(); 

return 0;
}

My structures:

#pragma pack(1)
typedef struct{
  uint32_t value : 24;
}bit24;
#pragma pack(0)


// Billedet
#pragma pack(1)
typedef struct{
  unsigned int Width;
  unsigned int Heigh;
bit24* RGB;
}Image;
#pragma pack(0)


typedef struct {
  BMP_FileHeader fileHeader;
  BMP_InfoHeader infoHeader;
  Image data;
 }BMP_Data;

My source main source code:

// the pic is a type of BMP_Data. sorry if i this is really messy.
int main( int argc, char *argv[] ){
setup_settings();

pic.data.Heigh = pic.infoHeader.biHeight;
pic.data.Width = pic.infoHeader.biWidth;

int bytesPerRGB = (pic.infoHeader.biBitCount/8);

//padded bytes?
int paddedBytes = ( pic.data.Width * bytesPerRGB) % 4;
printf("PaddedBytes: %d\n", paddedBytes);


pic.data.RGB = new bit24[ pic.data.Heigh * pic.data.Width * bytesPerRGB];

uint8_t r,g,b;
r = 0xFF;
g = 0xFF;
b = 0xFF;

/*
for( unsigned int y = 0; y < pic.data.Heigh; y++)
    for( unsigned int x = 0; x < pic.data.Width; x++)
    {
        pic.data.RGB[x + (y*pic.data.Width )].value = ( (b << 0) | (g << 8) | (r << 16) );
    } 
    */

for( unsigned int i = 0; i < pic.data.Heigh * pic.data.Width * bytesPerRGB; i+=3){
    pic.data.RGB[i ].value = ( (b << 0) | (g << 8) | (r << 16) );
}

SaveBitmapFile(FileName, pic.data.RGB);
delete [] pic.data.RGB;

return 0;
}

Answer 1

Okay, I have found the problem.

After I changed the bit24 to:

typedef struct{ 
uint8_t blue;
uint8_t green;
uint8_t red;
}RGB_Data;

from:

#pragma pack(1) 
typedef struct{
uint32_t value : 24;
}bit24;
#pragma pack(0)

and a little change in the main:

for( unsigned int i = 0; i < pic.data.Heigh * pic.data.Width * bytesPerRGB; i++){
    pic.data.RGB[i].blue  = b;
    pic.data.RGB[i].green = g;
    pic.data.RGB[i].red   = r;
}

it worked like a charm. thanx you for your help :)

Answer 2

You MUST fill all BitmapInfoHeader fields. - Assuming you want 24bits bitmap:

BITMAPINFOHEADER bi =
{
    sizeof(BITMAPINFOHEADER), // DWORD, = 40
    WIDTH, // DWORD, image width in pix
    HEIGHT, // DWORD, image width in pix
    1, // WORD, planes MUST be 1
    24,// WORD, num of bits per pixel
    BI_RGB, // DWORD, (no compression = BI_RGB = 0)
    0, // DWORD, sizeof image data, can be 0 if BI_RGB = 0
    0, // DWORD, x-resolution
    0, // DWORD, y-resolution
    0, // DWORD, colors used (palette images only)
    0, // DWORD, importand colors (palette images only)
};

Also make sure every row (horizontal line) of pixels is padded to multiple of 4 bytes !!!

(So begin with images of N x 4 width - they have no padding issues)